My Boots, who is now seven months old, was feral as well when I got him at 2 months old.
He hissed and hissed at me when I first got him, and wouldn't let me touch him hardly at all. I kept him separate in just one room, the bathroom, until I knew he could get along with my other adult cat, Kramer. That's my best advice: whenever you or a family member has free time, take Chance into the bathroom with you, shut the door, sit on the floor, and either do something else (read a book, play on a laptop, do your taxes, etc) or play with him with toys and treats for a while. I would recommend at least an hour of this per day, more if you have the time. If he's very scared, and hiding behind the toilet, don't reach for him or force him to come out. Let him come to you; he'll let you know when he's ready to play. Kittens get bored very easily.
He'll be scared at first, but eventually he'll realize that you're not a big mean monster coming to eat him. Being closer to his level helps; that's why I recommend sitting on the floor, because few things scared Boots more than me towering over him and reaching down to pet him. Cats think of space more vertically than we do, which is why they love climbing things and being on cat trees. Don't skimp on the treats; he might be very food-motivated, which will cause him to associate you, which he's not sure about yet, with treats, which he might love. This is a good thing.
Now, I can't promise that this will transform him into an easygoing, stranger-loving lap cuddler. Boots is still quite scared of most people that aren't me, although he does like at least a little lap time every day. (I live alone.) But if each family member does it, in time, he'll most likely come to tolerate everyone. He'll probably also bond specially with one member of your family, though that doesn't mean he doesn't love the rest of you